using System.ComponentModel;

namespace FluidExplorer.Services.Operations;

public enum FileOperationKind
{
    Copy,
    Move,
    Delete,
    Recycle,
    Rename,
    NewFolder
}

public enum JobState
{
    Queued,
    Running,
    Paused,
    Completed,
    CompletedWithErrors,
    Cancelled,
    Failed
}

public enum ConflictPolicy
{
    /// <summary>交给 UI 决定（ConflictResolver）。</summary>
    Ask,
    Replace,
    Skip,
    KeepBoth,
    Merge
}

public enum ConflictResolution
{
    Replace,
    Skip,
    KeepBoth,
    Cancel
}

public sealed class ConflictInfo
{
    public required string SourcePath { get; init; }
    public required string DestinationPath { get; init; }
    public bool SourceIsDirectory { get; init; }
    public long SourceSize { get; init; }
    public long DestinationSize { get; init; }
    public DateTime SourceModifiedUtc { get; init; }
    public DateTime DestinationModifiedUtc { get; init; }
    /// <summary>true 表示用户勾选了"为后续所有冲突执行相同操作"。</summary>
    public bool ApplyToAll { get; set; }
}

/// <summary>队列里的一个作业：可暂停/继续/取消，进度实时上报（含速度与剩余时间）。</summary>
public sealed class FileOperationJob : INotifyPropertyChanged
{
    private JobState _state = JobState.Queued;
    private int _completedItems;
    private long _completedBytes;
    private string? _currentItem;
    private string? _error;
    private double _bytesPerSecond;
    private bool _isIndeterminate;

    public Guid Id { get; } = Guid.NewGuid();
    public required FileOperationKind Kind { get; init; }
    public required string Title { get; init; }
    public required IReadOnlyList<string> Sources { get; init; }
    public string? Destination { get; init; }
    public ConflictPolicy Policy { get; init; } = ConflictPolicy.Ask;
    public bool PermanentDelete { get; init; }
    public string? NewName { get; init; }
    public DateTime StartedUtc { get; } = DateTime.UtcNow;

    public JobState State
    {
        get => _state;
        set => Set(ref _state, value);
    }

    public int TotalItems { get; set; }
    public int CompletedItems { get => _completedItems; set => Set(ref _completedItems, value); }
    public long TotalBytes { get; set; }
    public long CompletedBytes { get => _completedBytes; set => Set(ref _completedBytes, value); }
    public double BytesPerSecond { get => _bytesPerSecond; set => Set(ref _bytesPerSecond, value); }
    public string? CurrentItem { get => _currentItem; set => Set(ref _currentItem, value); }
    public string? Error { get => _error; set => Set(ref _error, value); }

    /// <summary>大小为 0 的作业（纯重命名等）显示旋转指示器。</summary>
    public bool IsIndeterminate { get => _isIndeterminate; set => Set(ref _isIndeterminate, value); }

    public double Progress => TotalBytes > 0
        ? Math.Clamp((double)CompletedBytes / TotalBytes, 0, 1)
        : (TotalItems > 0 ? Math.Clamp((double)CompletedItems / TotalItems, 0, 1) : 0);

    public TimeSpan? Eta => BytesPerSecond > 1 && TotalBytes > CompletedBytes
        ? TimeSpan.FromSeconds((TotalBytes - CompletedBytes) / BytesPerSecond)
        : null;

    public bool CanPause => State is JobState.Running or JobState.Paused;
    public bool CanCancel => State is JobState.Queued or JobState.Running or JobState.Paused;
    public bool IsFinished => State is JobState.Completed or JobState.CompletedWithErrors or JobState.Cancelled or JobState.Failed;

    public event PropertyChangedEventHandler? PropertyChanged;

    internal void RaiseAll()
    {
        foreach (var name in new[] { nameof(State), nameof(CompletedItems), nameof(CompletedBytes), nameof(BytesPerSecond),
                                     nameof(CurrentItem), nameof(Error), nameof(Progress), nameof(Eta),
                                     nameof(CanPause), nameof(CanCancel), nameof(IsFinished), nameof(IsIndeterminate) })
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }

    private void Set<T>(ref T field, T value, [System.Runtime.CompilerServices.CallerMemberName] string? name = null)
    {
        if (EqualityComparer<T>.Default.Equals(field, value)) return;
        field = value;
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }
}

public sealed class UndoEntry
{
    public required string Description { get; init; }
    public required FileOperationKind Kind { get; init; }
    /// <summary>(原路径, 现路径) 对；撤销即反向搬运。</summary>
    public required List<(string From, string To)> Moves { get; init; }
    /// <summary>删除操作记录：回收站里的 $R 文件路径 → 原始路径。</summary>
    public List<(string RecyclePath, string OriginalPath)> Deleted { get; init; } = [];
}

public sealed record OperationResult(bool Success, int Succeeded, int Failed, int Skipped, string? Error = null);

/// <summary>
/// 文件操作引擎：所有操作进入统一队列串行/并行执行，UI 永不阻塞。
/// 支持暂停、继续、取消、冲突策略、错误重试，以及一步撤销（Ctrl+Z）。
/// </summary>
public interface IFileOperationService
{
    IReadOnlyList<FileOperationJob> Jobs { get; }
    event EventHandler? JobsChanged;

    /// <summary>UI 设置此回调以弹出冲突对话框；未设置时按 KeepBoth 处理。</summary>
    Func<ConflictInfo, Task<ConflictResolution>>? ConflictResolver { get; set; }

    FileOperationJob EnqueueCopy(IReadOnlyList<string> sources, string destination, ConflictPolicy policy = ConflictPolicy.Ask);
    FileOperationJob EnqueueMove(IReadOnlyList<string> sources, string destination, ConflictPolicy policy = ConflictPolicy.Ask);
    FileOperationJob EnqueueDelete(IReadOnlyList<string> paths, bool permanent = false);
    FileOperationJob EnqueueRename(string path, string newName);
    FileOperationJob EnqueueNewFolder(string parentDirectory, string name);

    void Pause(Guid jobId);
    void Resume(Guid jobId);
    void Cancel(Guid jobId);
    void ClearFinished();

    bool CanUndo { get; }
    string? UndoDescription { get; }
    event EventHandler? UndoStackChanged;
    Task<OperationResult> UndoAsync(CancellationToken cancellationToken = default);

    /// <summary>计算源集合的总大小与条目数（后台执行，用于进度条与冲突提示）。</summary>
    Task<(long Bytes, int Items)> MeasureAsync(IReadOnlyList<string> paths, CancellationToken cancellationToken);
}